dns.subproj/res_query.c

   1 /*
   2  * Copyright (c) 1999, 2012-2018 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Portions Copyright (c) 1999 Apple Computer, Inc.  All Rights
   7  * Reserved.  This file contains Original Code and/or Modifications of
   8  * Original Code as defined in and that are subject to the Apple Public
   9  * Source License Version 1.1 (the "License").  You may not use this file
  10  * except in compliance with the License.  Please obtain a copy of the
  11  * License at http://www.apple.com/publicsource and read it before using
  12  * this file.
  13  *
  14  * The Original Code and all software distributed under the License are
  15  * distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  16  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  17  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  18  * FITNESS FOR A PARTICULAR PURPOSE OR NON- INFRINGEMENT.  Please see the
  19  * License for the specific language governing rights and limitations
  20  * under the License.
  21  *
  22  * @APPLE_LICENSE_HEADER_END@
  23  */
  24
  25 #include "libinfo_common.h"
  26
  27 #include <dns_sd.h>
  28 #include <errno.h>
  29
  30 #include <arpa/nameser_compat.h>
  31 #include <nameser.h>
  32
  33 #include "si_module.h"
  34
  35 extern int h_errno;
  36
  37 // Storage for the global struct __res_9_state.
  38 // The BIND9 libresolv.dylib shares the same storage for this structure as the
  39 // legacy BIND8 libsystem_info.dylib. This implementation does not require the
  40 // _res structure but libresolv.dylib does and many 3rd-party applications
  41 // access this global symbol directly so we preserve it here.
  42 #ifdef __LP64__
  43 #define RES_9_STATE_SIZE 552
  44 #else
  45 #define RES_9_STATE_SIZE 512
  46 #endif
  47 LIBINFO_EXPORT
  48 char _res[RES_9_STATE_SIZE] = {0};
  49
  50 LIBINFO_EXPORT
  51 int
  52 res_init(void)
  53 {
  54         // For compatibility only.
  55         return 0;
  56 }
  57
  58 // Perform a DNS query. Returned DNS response is placed in the answer buffer.
  59 // A preliminary check of the answer is performed and success is returned only
  60 // if no error is indicated in the answer and the answer count is nonzero.
  61 // Returns the size of the response on success, or -1 with h_errno set.
  62 static int
  63 _mdns_query(int call, const char *name, int class, int type, u_char *answer, int anslen)
  64 {
  65         int res = -1;
  66         si_item_t *item;
  67         uint32_t err;
  68         int cpylen = 0;
  69
  70         si_mod_t *dns = si_module_with_name("mdns");
  71         if (dns == NULL) {
  72                 h_errno = NO_RECOVERY;
  73                 return -1;
  74         }
  75
  76         item = dns->vtable->sim_item_call(dns, call, name, NULL, NULL, class, type, &err);
  77
  78         if (item != NULL) {
  79                 si_dnspacket_t *p;
  80
  81                 p = (si_dnspacket_t *)((uintptr_t)item + sizeof(si_item_t));
  82
  83                 res = p->dns_packet_len;
  84
  85                 if (res >= 0 && anslen >= 0) {
  86                         // Truncate destination buffer size.
  87                         memcpy(answer, p->dns_packet, (cpylen = MIN(res, anslen)));
  88                 }
  89                 else {
  90                         h_errno = NO_RECOVERY;
  91                         res = -1;
  92                 }
  93
  94                 si_item_release(item);
  95         } else {
  96                 h_errno = HOST_NOT_FOUND;
  97                 res = -1;
  98         }
  99
 100         if (cpylen >= sizeof(HEADER)) {
 101                 HEADER *hp = (HEADER *)answer;
 102                 switch (hp->rcode) {
 103                         case NXDOMAIN:
 104                                 h_errno = HOST_NOT_FOUND;
 105                                 res = -1;
 106                                 break;
 107                         case SERVFAIL:
 108                                 h_errno = TRY_AGAIN;
 109                                 res = -1;
 110                                 break;
 111                         case NOERROR:
 112                                 if (ntohs(hp->ancount) == 0) {
 113                                         h_errno = NO_DATA;
 114                                         res = -1;
 115                                 }
 116                                 break;
 117                         case FORMERR:
 118                         case NOTIMP:
 119                         case REFUSED:
 120                         default:
 121                                 h_errno = NO_RECOVERY;
 122                                 res = -1;
 123                                 break;
 124                 }
 125         }
 126
 127         si_module_release(dns);
 128         return res;
 129 }
 130
 131 LIBINFO_EXPORT
 132 int
 133 res_query(const char *name, int class, int type, u_char *answer, int anslen)
 134 {
 135         return _mdns_query(SI_CALL_DNS_QUERY, name, class, type, answer, anslen);
 136 }
 137
 138 LIBINFO_EXPORT
 139 int
 140 res_search(const char *name, int class, int type, u_char *answer, int anslen)
 141 {
 142         return _mdns_query(SI_CALL_DNS_SEARCH, name, class, type, answer, anslen);
 143 }